Autism is one of development disorders with impairment in sociality (prevalence is supposedly 1%). If incorrect diagnosis or detection of autism of a child may result in serious trouble in daily life and school life of the child and, in the child, lowering of self-esteem and development of psychiatric symptoms (such as anxiety and dysphoria) are predicted.
However, established effective medication of autism with has not yet been found. Therefore, the only way to achieve improve prognosis of autism is early diagnosis and early (from the age younger than 3 years old) educational intervention based on the diagnosis.
Currently, it is not easy to surely make early diagnosis of autism with standard clinical technique. In conventional diagnosis of autism, evaluation and diagnosis are conducted by a pediatrician or child psychiatrist based on behavior of infants. However, the number of the experts (specialists) is small and early diagnosis is difficult. Further, objective evaluation is currently difficult since the evaluation result varies depending on evaluators.
In current diagnosis of autism by specialists, experiential determination is made in interview based on appearance, or components of collected blood are examined. However, there is a problem in that the appearance-based determination requires a great deal of experience of specialists and is difficult to quantify. The blood test is accompanied with complication of blood collection. Further, in the examination of infants, these examination means are currently not effective and sure. This is because it is almost impossible to communicate with an infant in an interview and application of the determination based on blood components to an infant of younger than 3 years old is still in the laboratory stage. Further, there is a serious problem of failure or delay in medical consultation because parents of an infant do not detect whether or not the infant is an individual with autism.
In view of current situation above, with respect to autism of not only adults but also children (especially infants), a method, device and assistance system which enable early detection and early definite diagnosis by experts (specialists) based on objective evaluation are desired.
In recent years, it is becoming clear that abnormality is found in the distribution of points of regard of undiagnosed infants with autism. That is, it is becoming clear that an infant with autism is characteristic in that he/she cannot correctly draw attention to an eye gaze of another person. This abnormality is regarded as derived from the essence of autism, impairment in sociality. Further, this abnormality is regarded as a symptom appearing in an extremely early stage.
By the use of a preferable eye-gaze detection technique, this abnormality can be correctly detected and utilized as an objective index for early diagnosis of autism. Based on this idea, the present inventors focused on this abnormality.
In the obtainment of such abnormality in the distribution of points of regard, as a conventional eye-gaze detection technique, for example, a method for detecting eve gaze of a subject, using:
a first imaging camera for measuring the position of a pupil relative to a coordinate system;
a second imaging camera having a light source arranged at a known position in the coordinate system and forming a corneal reflection center to obtain data of a distance r from the corneal reflection center to a pupil center and an angle φ of distance r relative to a coordinate axis of the coordinate system; and
a calculation means for calculating the direction of eye gaze based on information from each of the cameras.
Further, some techniques using this method (device, technique and the like for detecting eye gaze) are also suggested (for example, see PATENT LITERATURES 1 to 5).
PATENT LITERATURE 6 discloses, as another technique similar to the “eye-gaze detection technique” of above-mentioned patented invention, an eye detection installation comprising:
one or more light sources for emitting light in directions toward the head of a user,
a detector for receiving light from the head of a user and to repeatedly capture pictures thereof, and
an evaluation unit connected to the detector for determining the position and/or gaze direction of an eye,
wherein the evaluation unit is arranged to determine, in a picture captured by the detector, an area in which an image of an eye or images of eyes is/are located and, after determining the area, to control the detector to forward to the evaluation unit information about successive or following pictures that only corresponds to the determined area of the image captured by the detector.
PATENT LITERATURE 7 discloses a device for recognizing eye gaze in which:
an eye is irradiated with light,
an image is formed by an imaging camera, the image having 3 or more characteristic points on the cornea of the eye,
the center of curvature of the cornea of the eye is determined from the characteristic points of the cornea on the formed image, and
the eye-gaze direction is recognized from the information of the center of curvature of the cornea and position of the center of the pupil,
the device comprising:
a provisional eye-gaze direction calculating means which calculates a provisional eye-gaze direction from the positional relationship between the center of curvature of the cornea and the center of the pupil,
a corneal area determining means which determines a restricted corneal area from the provisional eye-gaze direction and the information of the position of the pupil,
a treating means which, when the characteristic points on the image are present within the restricted corneal area, regards the provisional eye-gaze direction as the result of the recognition of eye gaze and, when a portion of the characteristic points on the image is not present within the restricted corneal area, selects additional characteristic points on the image present within the restricted corneal area, determines additional center of curvature of the cornea of the eye from the additional characteristic points on the image selected, recognizes additional eye-gaze direction from the information of the additional center of curvature of the cornea and position of the center of the pupil, and regards the additional eye-gaze direction as the result of the recognition of eye gaze.
PATENT LITERATURE 8 discloses an eye tracking system for monitoring the movement of a user's eye, the system comprising:    (a) video data input means for receiving video data produced by eye imaging means (imaging camera) monitoring the user's eye;    (b) spot location means for determining, from the video data, the location of a reference spot formed on the user's eye by illumination of the user's eye by a point source of light, the spot location means including adaptive threshold means for providing an indication of parts of the image produced by the eye imaging means which have a brightness greater than a threshold value, and spot identification means for selecting a valid reference spot by comparing the parts of the image with predetermined validity criteria;    (c) pupil location means for determining, from the video data, the location of the centre of the pupil of the user's eye relative to the reference spot in order to determine the user's line of gaze,
the pupil location means comprising:
a selection means which selects a pupil tracking window comprising a portion of the image produced by the eye imaging means, the portion corresponding to the location of the valid reference spot;
an edge selecting means which selects the edge of the pupil by selection of those parts of the gradient of the image portion in the pupil tracking window which have a gradient greater than a threshold value; and
a centre determining means which determines the centre of the pupil by referring to the points selected for the edge of the pupil;
the centre determining means comprising:
a triad selection means for substantially randomly selecting three superthreshold pixels to form a triad for further processing, from among a plurality of pixels of pupil image data; and
a triad processing means for determining the centre and radius of a hypothetical circle passing through each of the selected pixels; and    (d) display means for indicating the user's point of regard from the user's line of gaze determined by the pupil and spot location means.
However, any prior art in which the above-mentioned “eye-gaze detection technique” and the like using at least an Imaging Camera Portion is applied to assistance of diagnosis of autism has not yet been found.
Incidentally, as described later, in the present invention, an infant is characterized as an individual to which such an “eye-gaze detection technique” can be applied. Especially, each of the techniques of the above-mentioned PATENT LITERATURES 1 to 5 is one of the techniques suitable for an infant who has small pupils, cannot understand what is spoken and might not stand still as instructed.